Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965066AbWILId2 (ORCPT ); Tue, 12 Sep 2006 04:33:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965079AbWILId2 (ORCPT ); Tue, 12 Sep 2006 04:33:28 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.31.123]:31906 "EHLO atrey.karlin.mff.cuni.cz") by vger.kernel.org with ESMTP id S965066AbWILId1 (ORCPT ); Tue, 12 Sep 2006 04:33:27 -0400 Date: Tue, 12 Sep 2006 10:33:28 +0200 From: Pavel Machek To: Mark Gross Cc: kernel list , "Eugeny S. Mints" , Matthew Locke , Greg KH , Amit Kucheria , pm list , Preece Scott-PREECE , Igor Stoppa Subject: Re: cpufreq terminally broken [was Re: community PM requirements/issues and PowerOP] Message-ID: <20060912083328.GA19197@elf.ucw.cz> References: <450516E8.9010403@gmail.com> <20060911082025.GD1898@elf.ucw.cz> <20060911195546.GB11901@elf.ucw.cz> <4505CCDA.8020501@gmail.com> <20060911210026.GG11901@elf.ucw.cz> <4505DDA6.8080603@gmail.com> <20060911225617.GB13474@elf.ucw.cz> <20060912001701.GC14234@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060912001701.GC14234@linux.intel.com> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.11+cvs20060126 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2533 Lines: 51 Hi! > > > >No, there is reason to keep that in kernel -- so that cpufreq > > > >userspace interface can be kept, and so that resulting kernel<->user > > > >interface is not ugly. > > > Cpuferq defines cpufreq_frequency_table structure in arch independent > > > header while it's arch dependent data structure. A lot of code is built > > > around this invalid basic brick and therefore is invalid: cpufreq tables, > > > interface with cpu freq drivers, etc. Notion of transition latency as it > > > defined by cpufreq is wrong because it's not a function of cpu type but > > > function of current and next operating point. no runtime control on > > > operating points set. it's always the same set of operating points for all > > > system cpus in smp case and no way to define different sets or track any > > > dependencies in case say multi core cpus. insufficient kernel<->user space > > > interface to handle embedded requirements and no way to extend it within > > > current design. Shall I continue? Why should then anyone want to keep > > > cpufreq userspace interface just due to keep it? > > > > Yes, please continue. I do not think we can just rip cpufreq interface > > out of kernel, and I do not think it is as broken as you claim it > > is. Ripping interface out of kernel takes years. > > > > I'm sure cpufreq_frequency_table could be moved to asm/ header if you > > felt strongly about that. > > > > I believe we need to fix cpufreq if it is broken for embedded > > cases. > > cpufreq is broken at the cpufreq_driver interface for embedded > applications needing control over more than one control variable at a > time. > > That interface only supports setting target frequencies, and expanding it > to set target frequencies and voltages is not possible without something > like PowerOP. Adding the types of parameters to cpufreq would likely > make cpufreq a mess. Can we at least try adding that, before deciding cpufreq is unsuitable and starting new interface? I do not think issues are nearly as big as you think.. (at user<->kernel interface level, anyway; you'll need big changes under the hood). Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/